Cholesterol metabolism during cell growth: Which role for the plasma membrane?

Parenchyma proliferation is accompanied by a peculiar modification of the cholesterol metabolism involving both the growing tissue and the plasma compartment. The increase of cholesterol synthesis and uptake has been largely described in the literature and mainly ascribed to the increased requirement of cholesterol for new membrane biogenesis. The dramatic reduction of cholesterol efflux, which probably contributes to the increase of cholesterol esterification and accumulation, has also been largely described, although, further to acting as a prompt pool for membrane biogenesis requirements, its significance and possible influence on cholesterol homeostasis during growth has been almost completely neglected. In this short review, the most widely known modifications and new insights into the cholesterol metabolism during the growth of normal and tumoral cells will be discussed. Particular attention will be paid to the most widely known modifications of cholesterol storage and efflux. The possible implication of proteins in membrane cholesterol translocation causing cholesterol to be directed towards the ER for esterification by ACAT rather than being released by the appropriate external acceptor, i.e. HDL, during proliferation will be discussed.